Normalization of intraoperative parathyroid hormone does not predict normal postoperative parathyroid hormone levels.

Abstract

Intraoperative intact parathyroid hormone (iPTH) is being used to confirm complete excision of hyperfunctioning parathyroid tissue. It is uncertain whether normalization of intraoperative iPTH levels accurately predicts long-term postoperative iPTH values. Fifty-two consecutive patients with primary or secondary hyperparathyroidism underwent parathyroidectomy with measurement of intraoperative iPTH. Ten patients were excluded due to incomplete laboratory follow-up. Follow-up serum calcium and iPTH levels were measured at 1- and 3-month intervals. Before operation, the mean serum iPTH level was 249 pg/mL (SD=208) and mean serum calcium level was 11.4 +/- 0.9 mg/dL (+/- SD). In all but 4 patients, final intraoperative iPTH levels normalized to less than 67 +/- 41 pg/mL (mean, 35 pg/mL). One week after operation, serum calcium levels had returned to normal (mean, 9.4 +/- 1.1 pg/mL), which directly correlated with the final intraoperative serum iPTH values (Pearson correlation, r = -.434; P <.01). By 1 month, all but 2 patients were normocalcemic (mean, 9.4 +/- 0.9 pg/mL) with a mean iPTH level of 74.8 +/- 82 pg/mL. There was no correlation between final intraoperative and postoperative serum iPTH values (r =.099; P <.533). Both patients with persistent hypercalcemia at 1 month had appropriate intraoperative decreases in iPTH values. Intraoperative serum iPTH levels significantly correlate with postoperative serum calcium levels but not with postoperative serum iPTH levels. There was a 4.8% failure rate in the correction of postoperative serum calcium levels and a 29% failure rate in the normalization of postoperative serum iPTH levels.